Right. The author kind of sets him up for this point by joking that LaTeX would be better, and then walking it back.
Of course you could write docs in HTML with CSS if you wanted perfectly expressive syntax highlighting and context demarcation. And the opposite end of this would be arguing to use raw plaintext like an IETF specification.
But really Markdown is ubiquitous and represents a usable compromise between being readable as plaintext while enabling the 'progressive enhancement' of being converted to HTML.
Of course you could write docs in HTML with CSS if you wanted perfectly expressive syntax highlighting and context demarcation. And the opposite end of this would be arguing to use raw plaintext like an IETF specification.
But really Markdown is ubiquitous and represents a usable compromise between being readable as plaintext while enabling the 'progressive enhancement' of being converted to HTML.